A clause can contain any number of actions and variable
manipulations. If a clause is left empty, the default
action is taken. The default action is to trace the
enabled probe identifier (EPID) to the principal buffer. For
more information about epid
, see
Section 2.9.5, “Built-In Variables”. From the EPID, the
dtrace command outputs the following
information: CPU, probe ID, probe function, and probe name.
The default action facilitates a simple use of the
dtrace command. For example, running the
following command enables all of the probes in the
vmlinux
module with the default action:
# dtrace -m vmlinux
The preceding command might produce output similar to the following:
# dtrace -m vmlinux
dtrace: description 'vmlinux' matched 35 probes
CPU ID FUNCTION:NAME
0 42 __schedule:sleep
0 34 dequeue_task:dequeue
0 40 __schedule:off-cpu
0 23 finish_task_switch:on-cpu
0 24 enqueue_task:enqueue
0 41 __schedule:preempt
0 40 __schedule:off-cpu
0 23 finish_task_switch:on-cpu
0 11 update_process_times:tick
0 42 __schedule:sleep
0 34 dequeue_task:dequeue
0 40 __schedule:off-cpu
0 23 finish_task_switch:on-cpu
0 24 enqueue_task:enqueue
0 41 __schedule:preempt
0 40 __schedule:off-cpu
0 23 finish_task_switch:on-cpu
0 11 update_process_times:tick
0 12 try_to_wake_up:wakeup
0 42 __schedule:sleep
...